[decompiler] ensure names starting with numbers are escaped

^ KTIJ-25985

analysis/decompiled/decompiler-to-file-stubs/testData/clsFileStubBuilder/SpecialNames/SpecialNames.kt

@@ -0,0 +1,3 @@
+object SpecialNames {
+    val `1M` = 1
+}

analysis/decompiled/decompiler-to-file-stubs/testData/clsFileStubBuilder/SpecialNames/SpecialNames.txt

@@ -0,0 +1,13 @@
+PsiJetFileStubImpl[package=]
+  PACKAGE_DIRECTIVE
+  IMPORT_LIST
+  OBJECT_DECLARATION[classId=/SpecialNames, fqName=SpecialNames, isCompanion=false, isLocal=false, isObjectLiteral=false, isTopLevel=true, name=SpecialNames, superNames=[]]
+    MODIFIER_LIST[public]
+    CLASS_BODY
+      PROPERTY[fqName=SpecialNames.1M, hasDelegate=false, hasDelegateExpression=false, hasInitializer=false, hasReturnTypeRef=true, isExtension=false, isTopLevel=false, isVar=false, name=1M]
+        MODIFIER_LIST[public final]
+        TYPE_REFERENCE
+          USER_TYPE
+            USER_TYPE
+              REFERENCE_EXPRESSION[referencedName=kotlin]
+            REFERENCE_EXPRESSION[referencedName=Int]

analysis/decompiled/decompiler-to-file-stubs/tests/org/jetbrains/kotlin/analysis/decompiler/stub/files/ClsStubBuilderTestGenerated.java

@@ -246,6 +246,12 @@ public class ClsStubBuilderTestGenerated extends AbstractClsStubBuilderTest {
         runTest("analysis/decompiled/decompiler-to-file-stubs/testData/clsFileStubBuilder/SecondaryConstructors/");
     }
 
+    @Test
+    @TestMetadata("SpecialNames")
+    public void testSpecialNames() throws Exception {
+        runTest("analysis/decompiled/decompiler-to-file-stubs/testData/clsFileStubBuilder/SpecialNames/");
+    }
+
     @Test
     @TestMetadata("SuspendLambda")
     public void testSuspendLambda() throws Exception {

analysis/decompiled/decompiler-to-psi/tests/org/jetbrains/kotlin/analysis/decompiler/psi/ByDecompiledPsiStubBuilderTestGenerated.java

@@ -246,6 +246,12 @@ public class ByDecompiledPsiStubBuilderTestGenerated extends AbstractByDecompile
         runTest("analysis/decompiled/decompiler-to-file-stubs/testData/clsFileStubBuilder/SecondaryConstructors/");
     }
 
+    @Test
+    @TestMetadata("SpecialNames")
+    public void testSpecialNames() throws Exception {
+        runTest("analysis/decompiled/decompiler-to-file-stubs/testData/clsFileStubBuilder/SpecialNames/");
+    }
+
     @Test
     @TestMetadata("SuspendLambda")
     public void testSuspendLambda() throws Exception {

core/compiler.common/src/org/jetbrains/kotlin/renderer/RenderingUtils.kt

@@ -26,7 +26,10 @@ fun Name.render(): String {
 
 private fun Name.shouldBeEscaped(): Boolean {
     val string = asString()
-    return string in KeywordStringsGenerated.KEYWORDS || string.any { !Character.isLetterOrDigit(it) && it != '_' }
+    return string in KeywordStringsGenerated.KEYWORDS ||
+            string.any { !Character.isLetterOrDigit(it) && it != '_' } ||
+            string.isEmpty() ||
+            !Character.isJavaIdentifierStart(string.codePointAt(0))
 }
 
 fun FqNameUnsafe.render(): String {